EXPERIMENTAL STUDY OF STRESS CHANGES DUE TO COMPACTION GROUTING

抄録

In-situ static compaction by grouting is routinely used as a countermeasure against liquefaction in loose sandy ground. The surrounding ground's stress changes induced by grout injection are considered to be an important cause for the stabilisation effects, along with some densification of the ground in the bulb's vicinity. The present study investigates characteristics of the stress changes by simulating compaction grouting processes in a geotechnical centrifuge. Detailed descriptions are given of apparatus and experimental techniques specifically developed for conducting miniature injection tests. The observed increases in the horizontal stresses, evaluated in terms of the earth pressure coefficient, K, reflected the influence of grout pile spacing, and were found to be consistent with field measurements except near the surface. The centrifuge tests also allowed the changes in the dominant stress direction within the horizontal planes at the stabilised domain's centre to be evaluated, with the results indicating the dependency of the stress changes upon depth and interactions between neighboring grout piles. The significance of the stress changes in increasing the liquefaction resistance is demonstrated by mapping liquefaction curves against initial stress states through a series of cyclic hollow cylinder simple shear tests.